The present invention relates in general to penetrating radiant energy imaging and, more particularly, concerns a novel apparatus and techniques for selectively obtaining X-ray images of variable density contrast and/or spatial resolution with a modification of commercially available MICRO-DOSE.RTM. X-ray apparatus disclosed in U.S. Pat. No. 3,780,291, manufactured and sold by American Science and Engineering, Inc. The invention readily achieves magnification and greater resolution in the image of a scanned object with an improved scanning slit assembly.
The present invention represents an improvement of the invention in U.S. Pat. No. 3,780,291, embodied in the commercially available AS&E.RTM. MICRO-DOSE.RTM. X-ray imaging system used in airports and other locations for parcel inspection. In that system, a moving pencil beam of X-rays repeatedly scans a line detector as the scanned object is translated past the beam and detector assembly. The line detector produces light signals representative of the incident X-ray energy, which are then converted by photoelectric detecting means to video signals representative of the X-ray transmissivity between the beam source and the detector. From the video signals, a video system displays a sequence of horizontal lines to provide a two-dimensional image of the scanned object.
Four radial slits in a rotating disc of X-ray opaque material successively intercept the line beam to produce a pencil beam that scans the length of the line detector as the radial slits rotate; the intersection of one of the four slits and their corresponding line slit moves from one end of the line beam cross-section to the other.
It is an important object of this invention to provide an improved X-ray imagig system.
It is another object of the invention to achieve the preceding object with a system that provides increased density contrast as a trade-off against the size of the area of the object being imaged.
It is still another object of the invention to provide an improved X-ray imaging system that provides increased density contrast without decreasing the area of the object being imaged by increasing the number of detectors.
It is a further object of the invention to achieve one or more of the preceding objects with relatively slight modification of the prior art system described above.
It is still a further object of the invention to achieve one or more of the preceding objects by selectively displacing the relative position between the scanning slit assembly and the detector and X-ray source.
It is still a further object of the invention to achieve one or more of the preceding objects economically and with high reliability while permitting a relatively unskilled operator to easily effect the change in resolution/contrast.
It is still a further object of the invention to utilize essentially the same logic electronics for each of the images constructed using any of the line slit--radial slit combinations.
It is still a further object of the invention to have a fixed spatial relationship between the images formed by each line slit--radial slit combination, allowing a small area of one of the larger images to be easily X-rayed as higher density and/or spatial resolution.